CN104963098A - Method for preparing electrostatic spinning perfluocarbon polymer nanofiber membrane - Google Patents

Abstract

The invention discloses a method for preparing an electrostatic spinning nanofiber membrane. The method comprises the steps of A, preparing a spinning solution, wherein a spinning carrier solution the mass fraction of which is 6-15% is prepared, the spinning carrier solution is evenly mixed with a perfluocarbon polymer concentration dispersion emulsion according to a certain mass ratio, and absolute ethyl alcohol with a mixture weight percentage of 1-3% and a solution electrical conductivity conditioning agent with a mixture weight percentage of 0.05-0.1% are added so that the spinning solution can be obtained; B, preparing a precursor nanofiber membrane, wherein electrostatic spinning and drying are conducted on the spinning solution to obtain the precursor nanofiber membrane; C, preparing the perfluocarbon polymer nanofiber membrane, wherein high-temperature sintering is conducted on the precursor nanofiber membrane to obtain the perfluocarbon polymer nanofiber membrane. The prepared nanofiber membrane is of a three-dimensional network structure formed through nanofiber interlacing.

Description

A preparation method of electrospinning perfluoropolymer nanofiber membrane

technical field

The invention relates to the technical field of membranes, in particular to a method for preparing perfluoropolymer nanofiber membranes by electrospinning.

Background technique

Perfluoropolymers include polytetrafluoroethylene (PTFE), polyfluoroethylene propylene (FEP), polyperfluoroalkoxy (PFA), etc., which have the characteristics of stable chemical properties and excellent high and low temperature performance, and are more and more popular in membranes. The researchers' attention, especially its good corrosion resistance, is widely used in the separation of microparticles under harsh conditions. In addition, the strong hydrophobicity of perfluoropolymers makes them ideal materials for membrane distillation, membrane contactors, and osmotic distillation. Perfluoropolymer fibers were industrialized by DuPont in the mid-1950s with the trade name "Tenon (Teflon)". The company also successively developed FEP fiber in the 1960s, with the trade name "Teflon FEP", and "Teflon PFA" in the 1980s. Due to the special structure of perfluoropolymers, perfluoropolymer fibers are not suitable for conventional solution and melt spinning. Therefore, although perfluoropolymer fibers have been industrialized for more than 50 years, only a few companies have produced perfluoropolymer fiber products so far. There are four main spinning process routes: melt spinning, paste extrusion spinning, film split spinning and emulsion spinning. At present, the relatively mature method of preparing perfluoropolymer fibers in the world is the emulsion spinning method with polyvinyl alcohol or viscose fiber as the carrier (High-tech Fiber and Application, 1999, 05: 20-24.). Domestic Xiao Changfa used polyvinyl alcohol (PVA) as a film-forming carrier to prepare a PTFE hydrophobic film from a polyethylene dispersion emulsion (Polymer Materials Science and Engineering, 2010, 05: 123-126.). There have been many studies at home and abroad on the preparation of nanofiber separation membranes by electrospinning. Rong Wang used polyvinylidene fluoride (PVDF) to prepare nanofibrous membranes and applied them to direct contact membrane distillation, achieving good results. (Journal of Membrane Science. 425-426(2013) 30-39).

The preparation of traditional polymer fibers mainly adopts melt spinning and solution spinning, and the diameter of the fibers is generally more than ten microns. Electrospinning technology has received special attention in recent years because it can continuously produce polymer fibers with diameters of submicron or even nanometer. Because the diameter of the fiber reaches the nanometer level, the aspect ratio and specific surface area of the fiber are several orders of magnitude higher than those of traditional fibers, so it has a large specific surface area and porosity, and can be used for protective fabrics, filter materials, functional clothing, tissue engineering scaffolds, Biomedical materials and other fields. The present invention combines the characteristics of large specific surface area and small pore size of nanofiber membranes prepared by electrospinning and the characteristics of high temperature resistance and corrosion resistance of perfluoropolymers, and prepares perfluoropolymer nanofiber membranes by electrospinning. New ideas are put forward for the application field of fluoropolymer fibers.

Contents of the invention

Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a perfluoropolymer nanofiber membrane by electrospinning. The film is a precursor fiber film spun by electrospinning technology, and the nanofiber film material is obtained after high-temperature sintering. The obtained fiber membrane microscopically presents a three-dimensional network structure formed by interweaving nanofibers.

The technical solution of the present invention to solve the technical problem is: design a preparation method of electrospinning perfluoropolymer nanofiber membrane, comprising the following process steps:

A. Preparation of spinning solution

Prepare the spinning carrier solution with a mass fraction of 6-15%, and the spinning carrier and the perfluoropolymer concentrated dispersion emulsion with a solid content ratio of 1:2, 1:4, 1:6, 1:8 and 1:10 Mix evenly, and add 1 to 3% of absolute ethanol and 0.05 to 0.1% of solution conductivity modifier to prepare spinning solution; the mass concentration of the spinning carrier is 6 to 15%, and the spinning The carrier solvent is distilled water, the spinning carrier is polyvinyl alcohol with a low decomposition temperature, the degree of polymerization is 1700-2400, and the degree of alcoholysis is 88-99%; the weight solid content of the concentrated dispersion emulsion of the perfluoropolymer is 50 ~70%, the average particle size is 0.1-0.2 μm; the solution conductivity regulator is lithium chloride or sodium chloride.

B. Preparation of Precursor Nanofiber Membrane

The prepared spinning solution is injected into the electrospinning device, the spinning parameters are set, and the precursor nanofiber film is obtained after electrospinning and vacuum drying; the spinning parameters are: the voltage is 15-25KV, the spinneret The distance from the receiving tray is 8-25cm, the extrusion speed is 0.3-1mL/h, and the electrospun fibers are collected on the rotating circular shaft or flat plate; the drying temperature is 50-60°C, and the drying time is 8-12h.

C. Preparation of perfluoropolymer nanofibrous membranes

The precursor nanofiber membrane prepared by electrospinning is sintered at high temperature to obtain a perfluoropolymer nanofiber membrane; the sintering temperature is 280-390°C, the sintering time is 1-2min, and the heating rate is 1-10°C /min.

Compared with the prior art, the present invention uses polyvinyl alcohol as the spinning carrier, mixes the perfluoropolymer emulsion, prepares the precursor nanofiber membrane by electrospinning, and then sinters the precursor nanofiber membrane to prepare the perfluoropolymer The preparation method of the nanofiber membrane provided by the invention is simple and easy, and the prepared fiber membrane microscopically presents a three-dimensional network structure formed by interweaving nanofibers, and has uniform pore size distribution and high porosity.

Detailed ways

Below in conjunction with embodiment further specifically describe the present invention.

The electrospinning perfluoropolymer nanofiber membrane designed by the present invention comprises the following process steps:

A. Preparation of spinning solution

The spinning carrier solution with a mass fraction of 6-15% is prepared, and the spinning carrier and the perfluoropolymer concentrated dispersion emulsion are at a solid content ratio of 1:2; 1:4; 1:6; 1:8 and 1:10 Mix evenly, and add 1 to 3% of absolute ethanol and 0.05 to 0.1% of solution conductivity modifier to prepare spinning solution; the mass concentration of the spinning carrier is 6 to 15%, and the spinning The carrier solvent is distilled water, and the spinning carrier is a polymer with a low decomposition temperature; the weight solid content of the concentrated dispersion emulsion of the perfluoropolymer is 50-70%, and the average particle size of the particles is 0.1-0.2 μm; the conductivity of the solution is adjusted The agent is lithium chloride or sodium chloride.

In the above step A, the spinning carrier is a polymer with a low decomposition temperature, such as viscose and polyvinyl alcohol, among which water-soluble polyvinyl alcohol is more preferable. The spinning carrier of the embodiment is polyvinyl alcohol, its degree of polymerization is 1700-2400, and the degree of alcoholysis is 88-99%.

In the above step A, the purpose of adding absolute ethanol is to shorten the solidification time of the nanofibers, facilitate the formation of the fibers, and obtain a better fiber shape, and the dosage is generally 1-3% for the best effect. The purpose of adding the solution conductivity regulator is to increase the conductivity of the solution and improve the spinnability of the spinning solution, and the dosage is 0.05-1% for the best effect.

In the above step A, the spinning carrier and the perfluoropolymer concentrated dispersion emulsion have a solid content ratio of 1:2; 1:4; 1:6; 1:8 and 1:10 to prepare the precursor nanofiber membrane , the perfluoropolymer nanofiber membrane after sintering is optimal with 1:6 and 1:8, if the ratio is too small, the strength of the nanofiber membrane prepared is too low, if the ratio is too large, the spinneret is easy to block during spinning, The film is not uniform after sintering.

In the above step A, the perfluoropolymer concentrated dispersion emulsion is prepared by polymerizing the perfluoropolymer concentrated dispersion emulsion in the dispersion emulsion, or the perfluoropolymer is polymerized and dispersed in the dispersion liquid, and then the dispersion is concentrated liquid until the weight percent concentration of perfluoropolymer is 50-70%, to obtain concentrated dispersion emulsion. The concentrated perfluoropolymer dispersion can be prepared by itself, or a commercially available product can be used, and its performance parameters are listed in Table 1.

Table 1 Perfluoropolymer Concentrated Dispersion Emulsion Performance Parameter Values

B. Preparation of Precursor Nanofiber Membrane

The prepared spinning solution is injected into the electrospinning device, the spinning parameters are set, and the precursor nanofiber film is obtained after electrospinning and vacuum drying; the spinning parameters are: the voltage is 15-25KV, the spinneret The distance from the receiving tray is 8-25cm, the extrusion speed is 0.3-1mL/h, the electrospun fiber is collected by a rotating shaft (diameter 6cm, length 20cm), and the rotation speed is 500-900r/min; the drying temperature is 50-60°C , drying time is 8 ~ 12h.

In the above-mentioned step B, the voltage among the spinning parameters, the distance between the spinneret and the receiving tray, and the extrusion speed affect the shape and shape of the fiber. The spun precursor nanofiber membrane is put into a vacuum drum dryer, and vacuum-dried at 50-60° C. for 8-12 hours, so that the prepared precursor nanofiber membrane is dried and solidified to shape.

C. Preparation of perfluoropolymer nanofibrous membranes

The precursor nanofiber membrane prepared by electrospinning is sintered at high temperature to obtain a perfluoropolymer nanofiber membrane; the sintering temperature is 280-390°C, the sintering time is 1-2min, and the heating rate is 1-10 °C/min.

In the above step C, the high-temperature sintering process aims to burn off the spinning carrier in the precursor nanofiber membrane, and the sintering temperature must be higher than the decomposition temperature of the spinning carrier, and at the same time it must be near the melting point of the perfluoropolymer, so that the The perfluoropolymer interweaves into a three-dimensional network structure to form a nanofibrous membrane. The heating rate affects the formation of the final nanofibrous membrane. If the heating rate is too high, it will easily cause uneven heating and cracking of the membrane. Generally, the heating rate is preferably 1-10°C/min.

The preparation method of the present invention uses a perfluoropolymer, including mixing the spinning carrier with the concentrated dispersion of the perfluoropolymer, absolute ethanol, and a solution conductivity regulator in an appropriate proportion, and using the spinning carrier to prepare the precursor nanometer by electrospinning. The fiber membrane is then formed by vacuum drying the precursor, and finally undergoes high-temperature sintering and other processes to prepare a perfluoropolymer nanofiber membrane. Figure 1 is a scanning electron micrograph of the electrospun polytetrafluoroethylene nanofiber membrane prepared in the present invention.

What is not mentioned in the present invention is applicable to the prior art.

Specific examples of the present invention are given below, but the examples are only to further specifically illustrate the preparation method of the present invention, and do not limit the claims of the present invention.

Example 1

A. Preparation of spinning solution: 5 g of polyvinyl alcohol (type: 1788) was weighed and prepared into an aqueous solution with a mass fraction of 10%. Add 16.67g of polytetrafluoroethylene concentrated dispersion emulsion (corresponding to 26.46% of total solid content, PVA: PTFE ratio of 1: 2), keep stirring evenly, and stand for 12 hours for defoaming to obtain spinning solution.

B. Preparation of Precursor Nanofiber Membrane

The prepared spinning liquid is injected into a 5ml electrospinning syringe device, and the spinning parameters are set as follows: the voltage is 20KV, the distance between the spinneret and the receiving disc is 10cm, the extrusion speed is 8 μl/min, and the electrospinning fiber is collected by a rotating shaft ( Diameter 6cm, length 20cm), the rotating speed is 800r/min, and the precursor nanofiber membrane prepared is taken off from the drum after electrospinning for 6h. The spun precursor nanofiber membrane was placed in a vacuum drum dryer, vacuumed, and vacuum-dried at 60 °C for 12 h.

C. Preparation of perfluoropolymer nanofibrous membranes

Spread the dried precursor nanofiber film evenly on an iron plate covered with aluminum foil paper, put it into a muffle furnace, set the heating rate at 10°C/min, raise it to 380°C, keep it warm for 2min, and wait for it to cool down. After reaching room temperature, take it out to prepare a perfluoropolymer nanofiber membrane.

Example 2

A. Preparation of spinning solution: 5 g of polyvinyl alcohol (type: 1788) was weighed and prepared into an aqueous solution with a mass fraction of 10%. Add 50 g of polytetrafluoroethylene concentrated dispersion emulsion (equivalent to a total solid content of 35.00%, wherein PVA: PTFE is 1: 6), continue to stir evenly, and stand for 12 hours for defoaming to obtain a spinning solution.

B. Preparation of Precursor Nanofiber Membrane

Inject the prepared spinning liquid into a 5ml electrospinning syringe device, set the spinning parameters as follows: the voltage is 25KV, the distance between the spinneret and the receiving plate is 8cm, the extrusion speed is 8μl/min, and the electrospinning fiber is collected with flat conductive glass , The prepared precursor nanofiber membrane was removed from the drum after electrospinning for 3 h. The spun precursor nanofiber membrane was placed in a vacuum drum dryer, vacuumed, and dried at 60°C for 12 h.

C. Preparation of perfluoropolymer nanofibrous membranes

Spread the dried precursor nanofiber film evenly on an iron plate covered with aluminum foil paper, put it into a muffle furnace, set the heating rate at 1°C/min, raise it to 380°C, and keep it warm for 2min. After cooling down to room temperature, take it out to prepare a perfluoropolymer nanofiber membrane.

Example 3

A. Preparation of spinning solution: 2 g of polyvinyl alcohol (type: 1799) was weighed and prepared into an aqueous solution with a mass fraction of 8%. Add 26.67g of polytetrafluoroethylene concentrated dispersion emulsion, (equivalent to 34.84% of total solid content, wherein PVA:PTFE is 1:8), add lithium chloride 0.05g (accounting for 0.1% of the total mass), add absolute ethanol 1.55 ml (accounting for 3% of the total mass), after continuing to stir evenly, let stand for defoaming for 12 hours to obtain spinning solution.

B. Preparation of Precursor Nanofiber Membrane

The prepared spinning solution was injected into three 5ml electrospinning syringe devices, and the spinning parameters were set as follows: the voltage was 25KV, the distance between the spinneret and the receiving plate was 8cm, the extrusion speed was 6μl/min, and the electrospinning fiber was collected with a flat plate Conductive glass, the prepared precursor nanofiber film was removed from the drum after electrospinning for 3 h. The spun precursor nanofiber membrane was placed in a vacuum drum dryer, vacuumed, and dried at 60°C for 12 h.

C. Preparation of perfluoropolymer nanofibrous membranes

Spread the dried precursor nanofiber film evenly on an iron plate covered with aluminum foil paper, put it into a muffle furnace, set the heating rate at 1°C/min, raise it to 370°C, and keep it warm for 2min. After cooling down to room temperature, take it out to prepare a perfluoropolymer nanofiber membrane.

Example 4

A. Preparation of spinning solution: 2.5 g of polyvinyl alcohol (type: 1788) was weighed and prepared into an aqueous solution with a mass fraction of 10%. Add polyperfluoroethylene propylene concentrated dispersion emulsion (performance parameters (the same below): solid content (weight, the same below) 50±%, surfactant content (weight, the same below) 6±1wt%, pH value 8±1) 30g, (equivalent to total solid content 31.82%, wherein PVA: FEP is 1: 6), add lithium chloride 0.05g (accounting for 0.1% of total mass), add dehydrated alcohol 1.65ml (accounting for 3% of total mass) . After continuing to stir evenly, let stand for degassing for 12 hours to obtain spinning solution.

B. Preparation of Precursor Nanofiber Membrane

The prepared spinning solution was injected into three 5ml electrospinning syringe devices, and the spinning parameters were set as follows: the voltage was 20KV, the distance between the spinneret and the receiving plate was 8cm, the extrusion speed was 8μl/min, and the electrospinning fiber was collected by a flat plate Conductive glass, the prepared precursor nanofiber film was removed from the drum after electrospinning for 3 h. The spun precursor nanofiber membrane was placed in a vacuum drum dryer, vacuumed, and dried at 60°C for 12 h.

C. Preparation of perfluoropolymer nanofibrous membranes

Spread the dried precursor nanofiber film evenly on an iron plate covered with aluminum foil paper, put it into a muffle furnace, set the heating rate at 1°C/min, raise it to 280°C and keep it for 2min, and wait for it to drop to 280°C. After reaching room temperature, take it out to prepare a perfluoropolymer nanofiber membrane.

Example 5

A. Preparation of spinning solution: 2.5 g of polyvinyl alcohol (type: 1788) was weighed and prepared into an aqueous solution with a mass fraction of 15%. Mix and stir 30 g of polyperfluoroethylene propylene concentrated dispersion emulsion and polyvinyl alcohol aqueous solution (equivalent to a total solid content of 37.50%, wherein PVA:FEP is 1:6), and add 0.05 g of sodium chloride (accounting for 0.1% of the total mass) After adding 1.40ml of absolute ethanol (accounting for 3% of the total mass) and continuing to stir evenly, let it stand for 8 hours for defoaming to obtain a spinning solution.

B. Preparation of Precursor Nanofiber Membrane

Inject the prepared spinning liquid into a 10ml electrospinning needle and use needleless electrospinning, set the spinning parameters as follows: the voltage is 25KV, the distance between the spinneret and the receiving plate is 7cm, the extrusion speed is 20μl/min, and the electrospinning fibers are collected Using a flat conductive glass, remove the prepared precursor nanofiber membrane from the drum after electrospinning for 3 h. The spun precursor nanofiber membrane was placed in a vacuum drum dryer, vacuumed, and dried at 60°C for 12 h.

C. Preparation of perfluoropolymer nanofibrous membranes

Spread the dried precursor nanofiber membrane evenly on an iron plate covered with aluminum foil paper, put it into a muffle furnace, set the heating rate at 1°C/min, raise it to 280°C, keep it warm for 2min, and wait for it to cool down. After reaching room temperature, take it out to prepare a perfluoropolymer nanofiber membrane.

Claims (4)

1. a preparation method of electrospinning perfluoropolymer nanofiber membrane, is characterized in that the method comprises the following processing steps: A. Preparation of spinning solution Prepare the spinning carrier solution with a mass fraction of 6-15%, and the spinning carrier and the perfluoropolymer concentrated dispersion emulsion with a solid content ratio of 1:2, 1:4, 1:6, 1:8 and 1:10 mixing evenly, and adding 1 to 3% of absolute ethanol and 0.05 to 0.1% of a solution conductivity modifier to prepare a spinning solution; B. Preparation of Precursor Nanofiber Membrane Inject the spinning solution in step A into an electrospinning device, and obtain a precursor nanofiber film after electrospinning and vacuum drying; C. Preparation of perfluoropolymer nanofibrous membranes The precursor nanofiber membrane prepared by electrospinning is sintered at high temperature to obtain a perfluoropolymer nanofiber membrane; 2. according to the described electrospinning method perfluoropolymer nanofiber film of claim 1, it is characterized in that used spinning carrier is polyvinyl alcohol in the described step A, and perfluoropolymer emulsion is polytetrafluoroethylene (PTFE) Emulsion, perfluoroethylene propylene (FEP) emulsion or perfluoroalkoxy vinyl ether copolymer (PFA) emulsion. Wherein the polyvinyl alcohol is further characterized by a degree of polymerization of 1700-2400 and a degree of alcoholysis of 88-99%. The perfluoropolymer emulsion is further characterized by a solid content of 50-70% and an average particle diameter of 0.1-0.2 μm. 3. according to the described electrospinning method perfluoropolymer nanofiber film of claim 1, it is further characterized in that can add dehydrated alcohol, water-soluble inorganic substance porogen and solution conductivity adjustment in the spinning solution of described step A agent. The amount of the absolute ethanol is 1-3% of the weight of the mixed solution, and the used solution conductivity regulator can also be used as a water-soluble inorganic porogen to form dissolution pores after film formation, and is selected from water-soluble chloride salts, nitric acid Salt etc., preferably potassium chloride, sodium chloride, potassium nitrate, sodium nitrate, the consumption is 0.05～0.1% of the mixed liquid weight. 4. according to the described electrospinning method perfluoropolymer nanofiber film of claim 1, it is characterized in that in described step C, the sintering temperature of precursor nanofiber film is selected according to the difference of perfluoropolymer, is 280～ 390°C, the sintering time is 1-2min, and the heating rate is 1-10°C/min.